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  • Soil has been traditionally used for disposal of solid and liquid wastes. However, it has a limited capacity to absorb such wastes without impairing its productivity and thus it gives rise to soil pollution.
  • Soil degradation refers to deterioration and loss of productive capacity of soil for present and future use. It can be due to various reasons but those of most immediate concern are erosion, salinization, water logging and soil pollution.
  • Soil pollution arises because diffusion of pollutants is slow so that the pollution remains localized and in addition, the difficulties in measuring the availability of chemical contaminants in such a complex material as soil are much greater. The dereliction aspects of soil contamination are, however, most subtle and persistent contamination problem.

The major causes of soil pollution are:

  • Particle fallout of atmospheric contaminants, direct application of effluents and harmful chemicals such as fertilizers and pesticides and dumping of wastes.

 Major Sources of Soil Pollution and their Effects:

A major source of land pollution are the industries such as pulp and paper mills, oil refineries, power and heating plants, chemical and fertilizer manufacturing units, iron and steel plants, plastic and rubber producing complexes, etc. which dumps tones of solid wastes on land. Further, most industrial furnaces and thermal power plants produce fly ash, an important environmental pollutant. The effects of release of some major effluents on soil are highlighted below:-

  • Electroplating Industry

o    The electroplating industry is mainly involved in nickel, chromium and zinc plating processes. Where such effluents are used for irrigation, the heavy metals are likely to be taken up by plants and thus reach man and animals. Soil samples collected from land irrigated by trade effluent of electroplating industries show that the soil is more acidic in nature and has high toxic content.

  • Paper and Board Mills

o    Paper and Cardboard industry which is not using caustic for digestion is not toxic in nature but can change porosity of soil on indiscriminate application. However, agro based Paper mills contain large amounts of caustic which can increase salinity of soil.

o    From various studies it is clear that in case where only effluent is used for irrigation the percent sodium is much higher than in case where mixed irrigation (tube well water and effluent) is being used. High concentration of sodium reduces soil permeability and increases specific ion toxicity to crops.

  • Textile and Dyeing Units

o    Dyes are known to be carcinogenic in nature and effluents from textile and dyeing industries are known to contain unreacted dye in addition to detergents, organic and inorganic compounds.

  • Distillery Waste

o    Effluents from distillery units have high organic content and low pH.

o    Indiscriminate application generally results in aesthetic problems like imparting colour to the ground water and increasing acidity and concentrations of chloride, sulphate and conductance.

  • Mining

o    Area around smelting and mining complexes are usually soiled by metals such as cadmium, zinc, leads copper, arsenic and nickel due to industrial dust fall out.

o    These are not only phytotoxic even in small quantities but also render plants unsafe for human and animal consumption. Zinc often with cadmium is released in to environment during the course of breakdown of lubricating oils, vehicle tyres, galvanized metal and fertilizers.

  • Sewage

o    Disposal of sewage from municipal and commercial activities through open drains and channels which are often unlined can cause soil pollution due to lateral leaching. In several areas this waste water is used for irrigation which presents serious problems.

o    The continuous use of sewage effluents for irrigation of light textured soils increased metal concentrations in deeper soil layers. In Punjab the concentrations of Fe, Mn, Zn, Al and Ni were noted to be increased up to 60 cm depth (Brar et al., 2000).

o    This is especially because sewer waters contain detergents, pathogenic bacteria and even heavy toxic metals.

  • Agriculture

o    Modern agriculture has also considerably contributed to soil pollution through the non-judicious use of chemical fertilizers, herbicides, insecticides and fumigants.

o    Most of these are stable chemicals and remain in the soil for long periods without degradation, and have cumulative effect.

o    Pollution arising from pesticide usage has been a major cause of concern in the field of agriculture production.

o    Pesticide residues are found in soil, air and water as well as in living organisms. Apart from killing the living organism present on the surface of the soil, they reach the deeper layers through tilling and irrigation of the land killing still more living forms. There continuous use adversely affects soil productivity.


  •  Garbage

o    Quite a large amount of solid garbage is contributed by households in the form of municipal wastes.

o    These include both, bio-degradable and non-biodegradable substances which, if not properly disposed off, can become breeding places of rats, flies, bacteria, mosquitoes and a large number of other vectors, having the potential of causing many human diseases.  


    • The common methods of controlling soil pollution include:

    o    Composting of biodegradable waste which involves biological stabilization of solid matter under aerobic or anaerobic conditions. Organic manure is obtained which is an economically and ecologically useful product.

    o    Hydropulping of paper and food waste in which the waste is macerated and transported to a central facility for further treatment which includes dewatering and subsequent incineration.

    o    Incineration in which waste are burnt at high temperature with or without recovery of heat energy. This is a very suitable method for disposal of hazardous hospital waste and yields highest percent volume reduction. However it causes air pollution.

    o    Sanitary landfill is dumping of solid waste in a properly planned manner in low lying areas. The wastes are deposited and leveled in layers which are covered with 15-25 cm of soil and compacted after every dumping. This prevents harmful organisms to thrive on landfills and controls foul odour. These landfill sites are properly lined and designed to avoid water pollution problems due to longitudinal and lateral seepage of pollutants.

     Source: Department of Soil & Water Conservation, Punjab